The work aims to reveal failure mechanism of electrodes with TiB2-ZrB2/Ni coatings for spot welding galvanized steel sheet. Changes in surface structure, phase and properties of the coatings for spot welding galvanized steel sheet were characterized with scanning electron microscopy, X-ray diffractometer and microhardness test, respectively. Applying TiB2-ZrB2/Ni coatings to electrodes could significantly improve service life of spot-welding electrodes by nearly 5 times. Surface hardness of electrodes was obviously increased by the ZrB2-TiB2/Ni coatings, which slowed down plastic deformation on tips of coated elec?trodes. In addition, the ZrB2-TiB2/Ni coatings could mitigate alloying reaction between steel sheet coatings and spot-welding electrodes to some extent. The coatings will not drop off completely during the process of spot welding as ZrB2-TiB2/Ni-coated electrodes are of certain plasticity. The coatings acts until the electrodes fail, and primary form of electrode failure is plastic deformation.